Conventionally, as a vehicle air-conditioning apparatus having a dehumidifying heating function, there has been known a vehicle air-conditioning apparatus having the constitution disclosed in the following patent literature 1 (JP-A-6-341732).
As shown in FIG. 8, this vehicle air-conditioning apparatus includes a first heat exchanger 2 where a supply amount of air to the first heat exchanger is adjusted by a damper 5 and a second heat exchanger 3 which is arranged upstream of the first heat exchanger 2 in the inside of an air conditioning unit 1. A closed loop is formed by connecting a compressor 6, the first heat exchanger 2, a first expansion device 7, a vehicle exterior heat exchanger 4 arranged outside the air conditioning unit, an open/close valve V2, a second expansion device 41, the second heat exchanger 3 and an accumulator 10 by piping in this order. A passage which is opened or closed by an open/close valve V1 is provided between an inlet side and an outlet side of the first expansion device 7, a passage which is opened or closed by an open/close valve V3 is provided between an outlet side of the first heat exchanger 2 and an inlet side of the second expansion device 41, and a passage which is opened or closed by an open/close valve V4 is provided between an outlet side of the vehicle exterior heat exchanger 4 and a suction side of the compressor 6 (an inlet side of the accumulator 10). By controlling opening/closing of the respective open/close valves V1 to V4 and the degree of opening of the damper 5, an operation mode can be changed over among a cooling operation mode, a heating operation mode and a dehumidifying heating operation mode.
To be more specific, in the cooling operation mode, the open/close valve V1 is opened, the open/close valve V2 is opened, the open/close valve V3 is closed, and the open/close valve V4 is closed. The damper 5 is set at a full-cool position such that an air supply amount to the first heat exchanger 2 is set to 0, and all air which passes through the second heat exchanger is made to bypass the first heat exchanger 2. A refrigerant compressed by the compressor 6 is made to pass through the first heat exchanger 2 and, thereafter, heat of the refrigerant is radiated by the vehicle exterior heat exchanger 4, a pressure of the refrigerant is reduced by the second expansion device 41, and some heat is absorbed by the refrigerant at the second heat exchanger 3 and, thereafter, the refrigerant is made to return to the compressor 6 through the accumulator 10.
In the heating operation mode, the open/close valve V1 is closed, the open/close valve V2 is closed, the open/close valve V3 is closed, and the open/close valve V4 is opened. The damper 5 is set at a full-hot position such that all air which passes through the second heat exchanger 3 is made to pass through the first heat exchanger 2. Heat of the refrigerant compressed by the compressor 6 is radiated by the first heat exchanger 2 and, thereafter, a pressure of the refrigerant is reduced by the first expansion device 7 and some heat is absorbed by the refrigerant at the vehicle exterior heat exchanger 4 and, thereafter, the refrigerant is made to return to the compressor 6 through the accumulator 10.
In the dehumidifying heating operation mode, the open/close valve V1 is closed, the open/close valve V2 is closed, the open/close valve V3 is opened and the open/close valve V4 is opened. The damper is set at the full-hot position or at an intermediate position. As shown in FIG. 9, heat of the refrigerant compressed by the compressor 6 is radiated by the first heat exchanger 2 and, thereafter, a pressure of a part of the refrigerant is reduced by the second expansion device 41 and some heat is absorbed by the refrigerant at the second heat exchanger 3, while a pressure of a remaining part of the refrigerant is reduced by the first expansion device 7 and some heat is absorbed by the remaining refrigerant at the vehicle exterior heat exchanger 4 and, thereafter, the refrigerant is made to return to the compressor 6 through the accumulator 10.